Waterford — Long before Robert Lopez and Kristen Anderson-Lopez won Oscars and Grammys for writing the hugely popular songs for the movie phenomenon "Frozen," they were young artists developing work at the Eugene O'Neill Theater Center.

The married duo returned to the O'Neill for a Saturday gala where they were the honorees. Even though they were the ones being feted, Lopez (who co-created "The Book of Mormon") and Anderson-Lopez (whose "In Transit" will hit Broadway in November) paid tribute to the O'Neill, speaking about the significant impact the center has had on them.

Lopez recalled being at the center's National Music Theater Conference in 2002, developing "Avenue Q," which went on to become a huge hit and a Tony winner. The first night that "Avenue Q" was performed at the O'Neill, though, it didn't work, and Lopez and collaborators Jeff Marx and Jeff Whitty had to dive into revamping it.

"We spent a rather tumultuous couple of weeks working through and going from something that was a bunch of songs and a script into a show that worked," he said.

"I remember the tumult, but the years have kind of erased the specifics from my mind, and all that's left every time I come back now is the absolute magic and wonder of the grounds and the memories of when we all came together in the room and made something that all of a sudden worked and made theatrical magic here at the O'Neill."

He added, simply, "There would be no 'Avenue Q' without the O'Neill."

Anderson-Lopez and Lopez were dating then, and she came to visit him at the O'Neill. She said she ended up in awe of what was created, "watching 'Avenue Q' get birthed."

She got her own chance to be part of the renowned O'Neill process. She was an artist-in-residence in 2004 and developed "In Transit" with her co-creators James-Allen Ford, Russ Kaplan and Sara Wordsworth at the O'Neill's 2008 National Music Theater Conference.

"What was a collection of songs in five nights became a show that got optioned on Broadway on the Saturday night after we did our show," she said. "It's been a bit of journey since, but we're there."

Indeed, "In Transit" played off-Broadway back then but didn't transfer to Broadway. Later this year, though, a new production of "In Transit" will, in fact, open on Broadway.

And what better place than the O'Neill to work on "In Transit" as it gears up for that Broadway run? The creative team behind the show has been at the center since Wednesday, and they have overhauled the book and restructured things, according to Anderson-Lopez.

When she came to the O'Neill last week after being away for five years, Anderson-Lopez recalled, "There was, like, an orange moon hanging above the water, and there was the rustling of the trees, and it sort of felt like, 'OK, magic, come on!'"

Everyone talks about the magic of the O'Neill, she said. She views it this way: "The magic is somebody feeds you, you never have to worry about food. You're given a room and a piano, if you're doing musicals, and you're given a place to sleep. And you're given time, just time, away from New York, away from your children and your busy lives, away from all of that stuff, and there is a superpower focus that you get at the O'Neill. This really is a superpower. It's the only way these musicals with so many people can get done. ... When you support the O'Neill, you're actually giving an artist a superpower."

During Saturday's program, Preston Whiteway, executive director of the O'Neill, spoke about Lopez and Anderson-Lopez's joy in creating theater. When the center was launching its recent building campaign, Lopez and Anderson-Lopez signed on to outfit the space with a new piano. Whiteway announced at the gala that the O'Neill was going to name the large rehearsal room in the production cottage The Robert Lopez and Kristen Anderson-Lopez Studio.

Lopez and Anderson-Lopez both performed at the gala, as did some of the actors who starred in their works. Andrew Rannells, who played Elder Price in "The Book of Mormon" and went on to portray Elijah on HBO's "Girls," among other roles, soloed on "I Believe" from "The Book of Mormon" and dueted with Patti Murin on "Love Is An Open Door" from "Frozen." Jennifer Barnhart and Rick Lyon, both from the original Broadway production of "Avenue Q," sang a number that had been cut from the show called "Tear It Up." Betsy Wolfe wrapped up the night with, naturally, "Let It Go." (Reportedly, Wolfe will play Elsa and Murin will play Anna in "Frozen's" upcoming stage adaptation, which Lopez and Anderson-Lopez are working on.)

And the Lopez daughters, Katie, 11, and Annie, 7, made an appearance, too. They joined with Murin for "Do You Wanna Build a Snowman?" from "Frozen." Anderson-Lopez joked about that, saying, "This is the stage mother portion of our show. One of the things that is a big part of my life with Bobby and our family — we sing a lot. Our kids are a big part of our demos and a part of every song we write, if appropriate. We say, 'Hey, what do you think of this one we wrote today?' And if they want to hear it again, we're like, 'OK, we can send it to Disney.'"

After the gala, Anderson-Lopez said that the O'Neill holds a special place, too, because she and her husband really fell in love there.

"And there's something in the water — every time I came here for longer than five days, I ended up with a daughter," she said.